1. Field of the Invention
The present invention relates to a method and apparatus for controlling a motor of a disk drive, and more particularly, to a method of stably controlling the startup current of a motor in consideration of a voltage drop and a disk drive using the method.
2. Description of the Related Art
U.S. Pat. No. 5,412,809 discloses a circuit and a method for controlling current supplied to a disk drive, which can reduce power consumption associated with the startup of a spindle motor using a micro controller and a memory that stores current versus access time tables. Japanese Patent Laid-Open Publication No. hei 8-275579 discloses a method of driving a spindle motor by supplying power of a predetermined voltage from a power supply unit to a driving signal generating unit, detecting whether a frequency synchronized with the rotation of the spindle motor is within a predetermined range, and varying the driving voltage of the spindle motor if the frequency is outside the predetermined range.
Drives employing a spindle motor include hard disk drives (HDDs), compact disk-read only memory (CD-ROM) drives, digital versatile disk (DVD) drives, and so on. In general, if power is supplied to a disk drive, the disk drive enters an initial mode for starting a spindle motor to rotate a disk. To enable the initially static disk to reach a target rotating speed, much power consumption is required.
Accordingly, the disk drive consumes the most current when initially starting the spindle motor as shown in FIG. 4, and a voltage of power supplied to the disk drive drops due to the excessive current necessary for the initial startup of the spindle motor. If the voltage drops below a predetermined value, stable operation of the disk drive cannot be guaranteed. Accordingly, a power-on reset (POR) signal transits to a logic low level to restart the disk drive, as shown in FIG. 5.
If power supplied to the disk drive is unstable or the resistance of a power line in a printed circuit board (PCB) is large, a greater voltage drop occurs, such that the possibility that the power-on reset signal will transit to a logic low level at the startup of the spindle motor further increases.
Accordingly, if the voltage of power supplied for the startup of the spindle motor drops below a threshold value, the disk drive is repeatedly restarted due to the power-on reset signal, thereby making normal operation of the disk drive impossible.